Electric switch having arcing and current carrying contacts of bridging type



May 5, 1964 M. R. SWINEHART ELECTRIC SW ITCH HAVING ARCING AND CURRENTCARRYING CONTACTS OF BRIDGING TYPE 6 Sheets-Sheet 1 Filed Aug. 23, 1961IF iw Q: Q. a H 2 3 d n A I|||H 1 11R. H 0$ 8. H T 6 N u w 33 II (in I mH 3 m3 N 33 uw mum May 5, 1964 M. R. SWINEHART 3,132,225

ELECTRIC SWITCH HAVING ARCING AND CURRENT CARRYING CONTACTS OF BRIDGINGTYPE 6 Sheets-Sheet 2 Filed Aug. 23, 1961 mom wu #m mom mm s 3 fl 9 M IQ0 m 1 0M 0Q H 3m 3m mm mm u w 10m Q I mum M y 1964 M. R. SWINEHART3,132,225

ELECTRIC SWITCH HAVING ARCING AND CURRENT CARRYING CONTACTS OF BRIDGINGTYPE Filed Au hza, 1961 6 Sheets-Sheet C5 y 5, 1964 M R. SWINEHART3,132,225

ELECTRIC SWI'ICH HAVING ARCING AND CURRENT CARRYING CONTACTS OF BRIDGINGTYPE Filed Aug. 25, 1961 6 Sheets-Sheet 4 May 5, 1964 M. R. SWINEHART3,132,225

ELECTRIC s TCH HAVING ARC AND u T CARRY CONTACTS OF BR ING Filed Aug.25, 1961 6 Sheets-Sheet 5 y 5, 1964 M. R. SWINEHART 3,132,225

ELECTRIC SWITCH HAVING ARCING AND CURRENT CARRYING CONTACTS 0F BRIDGINGTYPE 6 Sheets-Sheet 6 Filed Aug. 25. 1961 United A States Patent.

This invention relates to electric switches and more particularly toelectricswitchesadapted for controlling large values of electric energy.

While not limited thereto, the inventionis especially applicable toelectromagnetic contactors for railroad locomotive service or the likewherein it is necessary to control and inteirupt high electric currents.I

7 An object of the invention is to provide an improved electric switchfor controlling high values of electric power.

A more specific object of the invention is toprovide an improvedelectric switch of the bridging contacts type.

Another specific object of the invention is to provide an improvedelectric switch having arcing contacts of the bridging type and currentcarrying contacts of. the bridging type to afford establishment of andinterruption of an electrical connection in two places in series therebyto enable control of higher power connections.

Another specific object of the invention is to provide improved arc hornmeans for an electric switch.

Another specific object of the invention is to provide improved arcshield means foran electric switch.

.A further specific object of the invention is to provide improved arcshield means having means to prevent arc damage thereto and affordingmore effective'insulation between the stationary and movable contacts.

Other objects and advantages of the invention will.

hereinafter appear. t

e The above mentioned and other objects and advantages of the inventionand the manner of obtaining them will best be understood by reference tothe following detailed description of anexemplary embodiment of anelectric switch taken in conjunction with the accompanying draw ings,wherein: p

FIGURE 1 is a front elevation view of an electrical contactorconstructed in accordance with the invention;

FIG. 2 is a right side elevation view of the contactor ofFIG. 1; t

FIG. 3 is a cross-sectional view, taken along line 3-3 of FIG; 1;

FIG. 4 is an exploded view of a portion of the contactor of FIG.'1; p v

FIG. 5 is an exploded view of another portion of the contactor of FIG.1; H

FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 1;

FIG. 7 is a cross-sectional view; of one side portion of the contactortaken along line 7-7 of FIG. 2;

FIG. 8 is a cross-sectional view of the taken along line 8-8 of FIG. 2;

FIG. 9 is a cross-sectional view of the portion of FIG. 7 taken alongline 9-9 of FIG. 2;

H6. .10 is an isometric view of a member constituting one-half of an arcshield showing the interior structure thereof; and

viewed'ifrom another direction.

Referring to FIGS. 1 and 2, there shown a mounting panel or base 2 ofelectrically insulating rnaterial for FIG.-1'l is an isometric view ofthe member of 'FIG. '10

supporting the contactor, the parts of the contactor being 1 secured tothe front surface asshown in FIG. 1 and to the portion of FIG. 7

left-hand surface of the panel as shown in FIG. 2 by bolts and screwsextending into and through the panel. I

The contactor is provided with an electromagnet comprising a coil 4having terminals 4a and 4b and a core '6 of magnetic material extendingtherethrough and rigidly secured to panel 2 and a pivotal armature 8 ofmagnetic material. The electromagnet is provided with means accessiblefrom the front of panel 2 to alford ready re. moval of coil '4. l'lhismeans comprises a washer 6a of larger diameter than the axial hole inthe coil for maintaining the coil on the core, a screw 6b or the likethreaded into an axial tapped hole in the free end of the core forretaining washer 6a in place and a slightly concave or dish-shapedrelatively fiat resilient spring washer 6c interposed between washer a:and coil 4 with the concave side thereoftoward the coil for pressing thecoil against its supporting bracket hereinafter described.

An L-shaped bracket 10 has the face of one angular portion dtla arrangedin parallel abutting relation to the lower portion of the front surfaceof panel 2 and another angular portion ltlb extending horizontallyfnom'the lower edge of the panel. A screw 12 extends through a suit--able hole in base 2 and a corresponding-hole 10c (FIG. 4) in angularportion 10a into threadedengagement in an axial tapped hole in the otherend of core ti to rigidly secure the core and bracket to the panel.Another screw 14 (FIG. 2) offset from screw 12 extends through asuitable hole in panel 2 into threaded engagement in a tapped hole ltld(FIG. 4) in angular portion 10a to prevent rotation of bracket 10 onscrew 12.

As shown in FIGS, 2, 3 and 4, angular portion ltlb of bracket 10 isprovided with means afiordin'g a pivotal seat for armature 8 comprisinga transverse bar 16- rigidly secured, as by welding, across the uppersurface thereshown in FIGS. .2 and 3 is mounted on the upper surface ofthe extreme end of angular portion ltlb of bracket 10 for use inelectrical interlocking or auxiliary circuits or the like. t Y

As in'FIGS. 2, 3 and 4, armature 8 is ct general ly flat configurationand is provided across its lower edge with an acute angular portionforming an elongated sharp edge 8a for pivoting in the substantiallyright angle between bar 16 and portion 10b of the bracket. This longpivot edge prevents wear at the armature pivot. Arma ture '8 isconfinedagainst lateral movement by a pair of pins 16a extending from bar 16 onopposite sides ofthe lower end of the armature. A dust seal 16b ofresilient or foam like rubber material is cemented along the uppersurface of bar 16. Seal t16b has its edge pressed into engagement withthe right-hand surface of armature 8 to seal the armature pivot fromadmission of dust or the like. A projection or plate 8b extendshorizontallyatl a substantially right angle from the face of armature 8'adjacent the lower end' thereof and is provided with a pair of enlarged,spaced holes '80 for freely accommodating bolts l3 when the armaturepivots. Holes'Bc are provided with counter bores as shown-in FIG. 4 foraccommodating resilient armature return means such as the lower ends ofhelical compression spnings 22 surround-ing the respective bolts. Theupper ends of \spn'nrgs 22 are stopped against suitable washers 18awhich are held in 3 place by nuts 18b threaded on the end-s of the boltsas shown in FIG. 3. SpringsZZ apply a force near the end of projection8b at a small angle relative to the major axis or plane of the armaturewhen the armature is open and bearing against its stop hereinafterdescribed thereby maintaining pivotal edge 8a of the armature biasedagainst bar 16 and in its seat. A lever or 8d extends from plate 8b atan upward angle and is provided through its free end with an adjustablebolt for engaging actuator 29a (FIG 1) for operating switch 20 when thearmature is actuated. Armature 8 is further provided with a threadedstud 8e extending horizontally froman upper portion of the left-handsurface thereof as shown in FIG. 4 for securing thereto a movablecontact assembly hereinafter described.

As shown in FIGS. 1, 3 and 5, a pair of stationary contacts 2.4 and 26are rigidly secured in spaced apart relation through respective terminalmembers hereinafter described to mounting panel 2. Each such stationarycontact is comprised of electrically conducting materials such as copperor the like and comprises a generally horizontal U-shaped configurationhaving an upper leg 24a, 26a and a lower leg 24b, 26b. The ends of lowerlegs 24b and 26b abut against respective terminal members 28 and 30 andare rigidly secured thereto by screws 32 and 34 extending through therespective terminal members to provide electrical connections. Upperlegs 24a and 26a are shorter than lower legs 24b and 26b and the endsthereof are spaced from terminal members 28 and 30 electrically toinsulate the same from the terminal members. Electrical connection ofthe terminal members to the lower legs of the stationary contactsaffords current flow in directions to aid blowout of the arcs ashereinafter more fully described. Screws 32 and 34 extend through holesin terminal members 218 and 30 into threaded engagement in tapped holesextending axially into lower legs 24b and 26b. Terminal members 28 and30 have first portions 28a and 30a extending upwardly along the face ofpanel 2 and second angular portions 28b and 30b extending over the upperedge of panel 2 beyond the rear surface of the panel. Portions 28b and3% of the terminal members are provided with suitable electricalconnectors 28c and 300 for connecting electrical conductors thereto.

Means are provided which are accessible from the front of panel 2 toafford ready removal of the stationary contacts. These means compriseterminal-s members 28 and 30 secured to panel, 2 by pairs of screws 28d,28a and 30d, Sile extending through holes in the upper and lower ends ofportions 28a and 30a of the terminal members and through correspondingholes in the panel into threaded engagement with suitable threadedsleeve inserts 2a pressed into the panel from the rear face thereof. Aswill be apparent, screws 28d, 282 and 30d, Site are accessible from thefront face 2b of the panel to facilitate removal of the stationarycontacts and terminal members when panel 2 is secured tosupportingstructure.

. 'Ihe lower portion of the yoke portion of each horizontal Ushapedstationary contact is provided on its outer surface with a recess filledwith an arcing contacting member 24c, 260 as shown in FIGS. 3 and 5.Immediately below such contacting member, there is provided downwardprojection 24d, 26d having a deeper recess partially filled with acurrent carrying contacting member Z4e, Zoe. These contacting membersare comprised of metal such as silver or the like having good electricalconducting properties. The step-like discontinuity between suchcontacting members on each stationary contact affords closure andopening of the arcing and current carrying contacts in the proper orderas hereinafter described.

tAS shown in FIGS. 2, 3 and 5, the windows formed by the U-shapedstationary contacts and the terminal members are substantially filledwith molded insulating material supporting members 36 and 38,respectively. Each such member is provided with a groove 36a, 38a aroundthree sides thereof as shown in FIG. for accommodating the associatedstationary contact and is rigidly secured to the associated terminalmember by a pair of screws 36b, 36c and 38b, 38c extending through theterminal member into threaded engagement in a pair of tapped holes inopposite corner portions thereof as shown in FIGS. 2 and 5.

Molded members '36 and 38 support are blowout magnets of the permanentmagnet type for the respective sides of an arcing contact bridgehereinafter described. For this purpose, elongated permanent magnets 40and 42 are embedded or molded in members 36 and 38, respectively, andextend transversely through the left-hand end portions of the latterslightly beyond the opposite sides thereof as shown in FIGS. 3, 5 and 9.A pair of non-magnetic pins 36d are molded in member '36 and a pair ofpins 38d are molded in member 38 for supporting magnet pole pieces. Thepins of each such pair are arranged parallel to the associated magnetabove and below the latter and are longer than the associated magnet sothat the ends thereof extend beyond the ends of the magnet. A pair ofgene-rally rectangular flat pole pieces 40a and 40b shown in 5 and eachhaving a pair of holes therein are thereby assembled on the oppositeends of pins 36d to engage the flat opposite ends of magnet 40. Similarpole pieces 42a and 42b shown in FIGS. 7, 8 and 9 are assembled on pins38d to engage the ends of magnet 42. The pairs of pole pieces may beheld in place by magnetic attraction but the opposite ends of the pairsof pins 36d and 38d may also be riveted over the pairs of pole pieces asshown in FIG. 9 to rigidly secure the same in place. As shown in FIGS. 2and 7, the pairs of pole pieces 40a, 40b and 42a, 42b extend on oppositesides of and beyond the respective arcing contacts to form magnetic airgaps across the latter to blow the electrical arcs when the contacts areopened into arc extinguishing horns hereinafter described.

As shown in FIGS. 3 and 4, a flat plate 44of insulating material isrigidly secured to the outer surface of armature 8, plate 44 having anarrower upper end portion 44a extending beyond the upper end of thearmature. An insulating sheet 46 having a configuration similar to thatof plate 44 is interposed between plate 44 and armature 8 for purposeshereinafter described. Stud 8e extends through holes 46a and 44b shownin FIG. 4 and is provided with suitable washers 48 and a nut 50 rigidlyto secure plate 44 and sheet 46 to armature 8. A spring pin 8 extendsfrom a hole in armature 8 through a hole in sheet 46 and partway into ahole in plate 441.20 p'revent rotation thereof on stud 8e. portion 44aof plate 44 is provided with a recess 446 to reduce the thicknessthereof for accommodating an elongated movable current carrying contactbridge 52, the edge of contact bridge 52 being confined against shoulder44d to maintain the contact bridge transversely on plate 44. The endsurfaces on one face of contact bridge 52 are provided with contactingmembers 52a comprising a metal having good electrical conductingcharacteristics such as silver or the like for engaging contactingmembers Me and 26e of the stationary contacts to bridge the latter whenthe electromagnet is'energized. As shown in FIGS. 4 and 6, an enlargedhead pin 54 extends through a. hole in the narrow portion 44a of plate44 and a hole in the midportion of contact bridge 52. A helicalcompression spring 56 surrounds pin 54 and is stopped against a washer54a surrounding pin 54 and a slotted-end adjusting nut 54b threaded onthe pin, there beinga retaining pin 54c extending through pin 54intermediate the ends thereof and through the slots to restrain the nutfrom rotating. Spring 56 resiliently presses contact 52 against plate 44in the recess thereof. The holein portion 44a of plate 44 is providedwith a counterbore 44h to accommodate the head of pin 54 and insulatingsheet 46 overlies the head of pin'54 to insulate the latter from theupper end of armature 8.

As shown in FIGS. 3 and 4, an arcing contact plate or bridge 58 overliescurrent carrying contact bridge 52 and The narrow end;

is resiliently secured to insulating plate 44. Contact plate 58 isprovided with a large hole 58afreely to clear nut 50. Contact plate 58is provided with a hole 58b adjacent the lower end thereofand anotherhole 580 adjacent one side thereof for freely receiving pins 441: and 44respectively, to hold contact plate 58 in registration with itssupporting insulating plate 44, pins44e and 44f being rigidly secured toinsulating plate 44. A short bushing 44g surrounds pin 44 to space thelower end of contact plate 58 from insulating plate 44 thereby to aifordrocking of the movable arcing contacting members on the stationarycontacting members when the armature is actuated and to attain largesurface area engagement between the movable'and stationary contactingmembers when the armature is in its attracted position.

As shown in FIG. 4, arcing contact plate 58 is generally U-shapedorbifurcated at its upper end and the end surfaces of one face of thebifurcated portions have secured thereto contacting members 58d of metalhaving good electrical conductivity such as silver or the like forengagement with contacting members 240- and 260 to bridge the stationarycontacts when the armature is attracted. The midportion of contact plate58 directly below the slot between the bifurcated portions is providedwith a hole 582 for freely accommodating'pin 54 and spring 56surrounding the latter. Hole 58:; is provided with a vcounterbore 58ffor accommodating one end of i a helical compression spring 66surrounding pin 54 and spring 56. The other end of spring 60 is stoppedagainst a steppedwasher 54d surrounding pin 54 and a slottedendadjustingnut 54e threaded on the end of the pin, there being aretaining pin 54fextending through pin 54 and throughthe slots in the nut as shown inFIG. 6 to re-.

strain the nut from turning. Spring 60 resiliently presses contactplate58 against contact bridge 52 as shown in As shown in FIGS. and 9, eachmolded member, such as members 36 and 38, is provided at its upper andlefthand end portions on opposite sides thereofwith grooves 36a, 38aforming a stepped portion for receiving. the

complementary portion of each arc shield 62, 64 shown in FIGS], 9 and11. Each arc shield 62 and 64 is formed of two complementary portions62a and 62b, 64a and 64b of insulating material secured to one anotherby a plurality of bolts 62c and 64c,.respectively, to form an.

enclosure. closed at the top and partially closed at the bottom andhavingopen ends. One complementary portion 64raof arc shield 64 is shownin FIGS. 10 and 11.

Portion64a is provided with a wall 64d along the upper portion thereoffor engagement with a complementary wall on the other portion as shownin FIGS. 1 and 9. A relatively shorter lower wall 642 is provided asshown in FIGS. 10 and 11 for engagement witha complementary lower wallon the other portion as shown in FIG. 1. The aforementitoned bolts 64cextend-through these upper and lowerwalls to clamp the two side portionstogether. A groove 64 is provided along the right-hand portion shown inFIG. 11 to provide a reduced portion for receipt in groove 38:: inmolded member 38 as shown inEIG. 9 to providethe arc shield withclose-fitting engagementaround the stationary contacts. As shown inFIGJ'I9, the arc shield 64 fits over molded member 38 betweenpthelatterand the'associated pole pieces 42a and 4212 so that the pole piecesextend. externally of and A clamping bar 66 having a clamping bolt 68extend ing therethrough and through mounting panel 2 is providedforclamping the arc shields in place, bolt 68 exte'ndingthrough the spacebetween the innermost opposed pole pieces 40b and 420 as shown inFIG. 1. Each arc shield is provided with a recess 62h, 64h for accombythe curved upper surface of the upper leg 24a, 26a of I each stationarycontact. One end of arc horn member 70 is adjacent stationary contact 26as shown in FIG. 3 and the other end extends externally of theassociated arc shield 64 and is providedwith an electrical connectorsuch as a bolt 70a or the like. The end of arc horn member 7li-adjacentstationary contact 26 is spacedfrom the stationary contact a shorterdistance than the distance between contact members 260 and 58d when thecontacts" are open as shown in FIG. 3 to improve the transfer of the arefrom the contacts to the arc horn when the contacts are-opened.

An electrical conductor 72 shown in FIG. 1 connects the external ends ofarc horn members 70 to one another and another electrical conductor 74connects the external end of one arc horn member 70'to bridging contactmem! ber 58 as most clearly shown in FIGS. 3 and 4. In this manner, archorn members 70 are maintained at the same electrical potential asbridging contact member 58.

A pair of bolts 76 are rigidly secured to mounting panel 2 and extendpast the opposite sides of armature 8 and the bridging. contactassembly. A stopping bar 78 is coi1-- nected across the ends of thesebolts to form a stop for the opening movement of the bridging contactswhen the electromagnet is deenergized. As shown in FIG. 3, one of thebolts 76 lies between coil terminals 4a and 4b to prevent the coil fromrotating. The bolts 76 are covered by insulating sleeves 76a to insulatethe bolt from the coil terminals As shown in FIGS. 2 and 3, mountingpanel 2 is provided with counter-bores on the rear face thereof to ac'commodate the ends of the bolts and threaded inserts which are securedthereto. An insulating sheet 80 overliesthese counter-sunk bolt endsexcept bolt 68 to insulate: the same from one another and from theconnector port1ons 28b and 30b of terminal members 28 and 30. Thelefthand end of bolt 68, as shown in FIG. 2, is provided with aremovable thumb screw 68a threaded intoan axial tapped hole in the endof a hexagonal portion 68b of the The rightbolt to facilitate removal ofthe arc shields. hand end of bolt 68 is provided with an annulargroove'for accommodating a retaining ring .680, there being a washer 68dbetweenretaining ring 68c and the bottom of the recess or counter-borein panel 2 The right-hand end Y of bolt 68 is threaded and extendsbeyondpanelz provid-q ing means for securing the contactor assembly toamounting structure or the like. The portion of bolt 68 immediatelyadjacent the front surface of panel 2 is hexagonal in shape so that itcan be gripped by a wrench and turned into a threaded hole in themounting structure. 7

As shownin FIGS. 10 and 11, each half portion of each of thetwo arcshields such as half portion 64a of arc" shield 64 is provided with anangularinternal wall 64g. The other half portion of each arc shield suchas portion 64b is provided with a complementary angular wall 64g shownin FIGS. 7 and 8. These two walls 64g and 64g engage one another alongtheir inwardly projecting edges completely to close the interior of thearc shield enclosure" throughout the length of these walls. These wallsin'each arc shield surround the end and the b ack of each leg of arcingcontact bridge 58 as shown in FIG.3. These walls prevent the are fromflashing between the rear side of the leg of the arcing contactbridgeand the rear side of the V arc horn member 70 thereby to enhancethe transfer of i the arc to the arc horn when the arcing contacts are iopened. I v v Each half portion of each arc shield is provided with anelongated cavity such as cavity 64k shown in FIGS. 3, I 7; .10 and 11.As shown in FIGS. 3 and 7, these cavities j are in registration with oneanother and extend along the inner surfaces of the arc shield in thearea in registration with the space between the arcing contacting memberand the associated stationary contact. More specifically, cavity 64k asshown in FIG. 3 extends in registration with the surface of stationarycontact member 26c from the lower end thereof between stationary contact26 and are horn member 70 slightly beyond the end of arc horn member 70.The purpose of these cavities 64k is to afford insulating surfacesperpendicular to the direction of the arc. Melted contact material isnot likely tobe deposited on these perpendicular surfaces and,therefore, these cavities prevent establishment of deposited materialconducting paths between the stationary contact and the arcing contactbridge and between the stationary contact and are horn member 7 0.

. As shown in FIGS. 3, 7, 8 and 11, groove 64 for are horn member 70 isprovided with a stepped upper wall to provide a narrow slot 641extending along are born member 70. This slot is small enough so thatthe are traveling along the horn does not enter therein. This slot isalso large enough so that deposited contact material or are hornmaterial will not bridge the space between arc horn member 70 and theinsulating interior wall of the arc shield. Such bridging of the archorn member by deposited material on the interior walls of the arcshield might cause the arc to hang up and cause burning of the arcshield. Slot 641 prevents such burning of the arc shield. a i

. As shown in FIGS. 7 and 9, a narrow slot 64m is provided between theopposite sides of each stationary contact such as contact 26 and theadjacent interior walls of the arc shield. These slots 64m extendthroughout the portions of the arc shields where such portions areadjacent the stationary contacts. The size of these slots 64m and theirpurpose are similar to that described in connection with slots 641 alongarc horn member 70. When operating coil 4 is energized, armature 8 isattracted to the end of core 6 having washer 6a secured thereto.Armature 8 pivots on edge 8a thereof in the clockwise direction to causecompression of return springs 22. The magnetic attraction of armature 8maintains pivot 8a thereof against bar 16, Arm 8d actuates switchZO.

Armature 8 carries the assembly" comprising insulatingsheet 46,insulating member 44, current carrying contact bridge 52 and arcingcontact plate 58. As armature 8 pivots in the clockwise direction, FIGS.2, 3 and 6, contacting members 580? of arcing contact plate 58 firstengage contactingmembers 24c and 260 of stationary contacts 24 and 26,respectively, to bridge the stationary contacts. As the armature pivotsfurther, current carrying contact bridge 52 separates from arcingcontact plate 58 and spring 60 is compressed. Spring 56, however,maintains current carrying contact bridge 52 in engagement withinsulating plate 44 to move with the latter. Itwill be apparent thatduring such further pivoting of the armature, arcing contact plate 58pivots on pin 44] relative to insulating plate 44 and that the pivotpoint, that is, pin 44 of arcing contact plate 58 moves toward the rightin FIG. 3. This imparts a rocking movement to contacting members 58a torock the same into'large area surface engagement with stationarycontacting members 240 and 260. Thereafter, contacting members 52a ofcurrent carrying contactbridge '52 engage stationary contacting membersMe and 26e to bridge the stationary contacts. Further pivoting of thearmature into engagement with washer Go on the end of core 6 causesspring 56 to be compressed as current carrying'contact bridge 52separates from insulating plate 44. Such separation of contact bridge 52and plate 44 allows contacting members 52a to settle into, large areasurface engagement with stationary contacting members 24c and 26e. Also,spring 56 maintains sufiicient contact pressure thei'ebetween toestablish a good electrical connection. When spring 56 is compressed asaforestated, spring 60 is compressed further:

contacts and into the arc horns.

to maintain suflicient contact pressure between the arcing contactingmembers. I

When coil 4 is deenergized, return springs 22 pivot armature 8 in thecounterclockwise direction to open the contacts and to interrupt theelectrical connection therethrough at two points in series. Whenarmature 8 starts to pivot, insulating plate 44 engages current carryingcontact bridge 52 to move the latter in the left-hand direction in FIG.3 and to disengage contact members 52a from stationary contactingmembers Me and 26e to interrupt the current carrying connection. Asarmature 8 starts to pivot as aforesaid, spring 56 maintains the currentcarrying contacts closed while the gap between insulating plate 44 andcontact bridge 52 closes. Insulating plate 44 first engages contactbridge 52 at the upper portion thereof as seen in FIG. 3. to impart tocontact bridge 52 a counterclockwise rocking movement. This tends tobreak any weld between the current carrying contacting members. As thearmature pivots further following opening of the current carryingcontacts, spring 60 maintains the arcing contacting members closed asthe gap between contact bridge 52 and contact plate 58 closes. Thispivoting of the armature also causes pivot pin 44f'to move in theleft-hand direction in FIG. 3 thereby to impart a clockwise rockingmovement to the arcing contacting members 53d. This tends to break anyweld between the movable and stationary contacting members. Aftercontact bridge 52 engages contact plate 58, the arcing contactingmembers open in response to the complete pivoting of the armature in theopeningdirection. During the clockwise and counterclockwise pivoting ofthe armature, springs 22 apply a force on the end of arm 8b in adirection tending to maintain pivotal edge 8a of the armature in itsseat against bar 16.

Permanent magnets 48 and 42 are polarized in opposite directions so thatthe arcs between the respective stationary contacts and the legs ofarcing contact plate .58 are blown in a direction away from the currentcarrying As the arcing contacting members 580! separate from thestationary contacts, the arcs drawn therebetween are blown upwardly inFIGS. 1, 2 and 3 by the magnetic fields produced by the permanentmagnets 40 and 42 between the pole pieces of the respective pairsthereof. The direction in which the arcs are moved is expressed byFlemings left-hand rule. According to this rule, if the forefinger ispointed in the direction of the flux between the pole pieces and themiddle finger is pointed inthe direction of the current in the arc, thethumb will point in the direction in which the arc will move.- Assumingthat in FIG. 3, the current flows downward in terminal 30 and in thelefthand direction in the lower leg 26b of the stationary contact andacross the gap into arcing contacting member 58d and out through theother terminal, then permanent magnet 42 must have a polarity of a northpole at its left end and a south pole at its right end as viewed in'FIG. 1 or a south pole at its near end and a north pole at its far endin FIG. 3. This polarity will cause the magnetic flux which passes fromnorth pole piece 42a transversely of the arcing contact gap to southpole piece 42b to move the arc upwardly. As the arc moves upwardly, wall64g in the arc shield prevents the are from striking between arcingcontact plate 58 and are horn member '70. As shown in FIG. 3, theright-hand end of arc horn member 70 is nearer stationary contact 26than is arcing contacting member 58d when fully open. This difference indistance between arc horn member 70 and stationary contact 26 relativeto the distance between 'contacting members 58d and 260 enhancestransfer-of the arc to the arc horn. The arc then moves outwardly alongthe upper surface of arc horn member 70 and the upper surface ofstationary contact 26 until it ruptures and is extinguished. Upper legs24a and 26a of stationary contacts 24 and 26, respectively, are shorterthan the lower legs 24b and 26b to provide an insulating air gap betweensuch upper legs and the respectively associated terminal members 28and'30. This air gap tends to prevent the arcs from running onto theterminal members.

The terminal membersare arrangedand constructed so that thecurrentsfiowing therein increase the magnetic force of the blowoutmagnets rather than decrease it. For example, current flowing downwardlyin terminal member30 in FIG. 3 develops magnetic lines of force passingin the clockwise direction aroundthe terminal member when viewed. fromabove according to the Arnperefruleu As permanent magnet 42 is polarizedwith a south pole at its near end a north at its far end in FIG. '5 andthe magnetic lines of force in a permanent magnet pass therethrough fromthe south end toward the north end, it will be apparent that thelines'of force developed by the current in the terminal members, are inthe same direction and, therefore, tend to increase the blowout effect.

As will be apparent, conductor 72 electrically connects arc horn members70 to maintain them at the same potential. Also, conductor 74 connectsarc horn members 70 to arcing contact plate 58 to maintain them at thesame potential thereby to facilitate transfer of the arcs from thearcing contacts to the arc horns under the action of the blowout.devices. Movable current carrying contact 52. is maintained inelectrical connection with.

movable arcing contact plate 58 through springs 56 and 6.0 and bolt .54.

.As will be apparenhuse of the arcing contacts which close first andopen last prevents arc damage to the current carrying, contacts. Thebridging contact construction enables the contactor to control largercurrents and voltages. This is for, the reason that'the electricalconnection is interrupted in two places simultaneously. As the circuitis'interrupted in twoplaces, the voltage across the opening contacts oneach side'of the bridging contact will be only one-half of what it wouldbe across a single interrupting contact.

The terminal members 300 are widely spaced from other metallic membersof the contactor to insulate the same from one another. The areshields62 and 64 are readily removable by removing thumb screw 68a andvclamping member 66 and conductor 74. Among other things, the stationarycontacts 24 and 26 are readily removablefr'om the front as seen in F16 1without re- 7 moving the contactor base 2 from its mounting structure towhich it may be secured by the threaded end of bolt 68. To removestationary contact26, it is only necessary to remove screws 39d and 30awhich are accessible from the front.- This permits removal of theassembly comprising terminal member 30, contact 26, molded member38,'rnag net 42 andpole pieces 4 2 aand 4213. This facili tatesreplacement of the stationary contacts" 24 and 26.

The threaded nuts 54b and Sqte on bolt 54 afford easy adjustment of theforces of springs 56 and 60. These nuts are provided with suitable slotsto accommodate locking pins 540 and 54 to lock the nuts in adjustedpositions. Use of alnico permanent magnets and 42 atfords strongmagnetic fields for extinguishing the arcs. Cavity 64k preventsdeposited contact material-from establishing an electrical path betweenthe contacts or between ing contact bridge for engaging said stationarycontacts to complete an electrical connection therethrough a movablesupporting member, and means mounting said arcing contact bridge andsaid current carrying contact bridge on said supporting member, andresiliently biasing themindependently against one side of saidsupporting member in stacked relation for successive separation from thelatter as said contact bridges close against said stationary contactswhereby said arcing contact bridge closes the connection first and opensthe connection last and said current carrying contact bridge closes. theconnection last and, opens the connection first across said stationarycontacts when said supporting member is moved inopposite directions, andsaid contact bridges each cause interruption of the connection betweensaid stationary contacts in two places thereby to afford interruption ofhigher voltage converging ends a distance less than the distancebetween,

the arcing contact bridge and the associated stationary contact in theiropen condition. a

5. The invention defined in claim 1, wherein each said stationarycontact is provided with a first portion for engagement by said arcingcontact bridge and a second portionufor engagement by said currentcarrying contact bridge, and the distance between said first portion andsaid arcing contact bridge is less than the distance be-. tween saidsecond portion and said current carrying con-1 tact bridge when saidcontact bridges are disengaged from said stationary contacts.

6. The invention defined in claim 1, together with an arc shield foreach side of said arcing contact bridge, each said are shield comprisingan enclosure of insulating material surrounding and covering theassociated stationary contact and the portion of said arcing contactbridge which engages the latter, and an electrically conducting membermounted Within each said enclosure forming with the associatedstationary contact an arc horn diverging from near the point ofengagement between saidarcing contact bridge and the associatedstationary contact.

7. The invention defined in claim 6, wherein each said are shieldenclosure comprises a closedinternal Wall between and separating saidelectrically conducting arc horn member from said arcing contact bridgeto prevent an electrical are from being established between said areborn the portions of the arc horn. And slots MI and 64m tend to preventthe arcs from burning the arc shields.

While the apparatus and structures hereinbefore described areeffectively adapted to fulfill the objects stated,

it is to be understood that I do not intend to confine my invention tothe particular preferred embodiment of elec- 'tric switch having arcextinguishing means disclosed,

inasmuch as it is susceptible of various modifications without departingfrom the scope of the appended claims.

I claim: 1. In an electric switch, two stationary contacts mounted inspaced apart relation, a movable arcing contact bridge for engaging saidstationary'contacts to complete an electrical connection therethrough, amovable current carrymember and the rear surface of said arcing contactbridge.

8. The invention defined in claim 6, together With a pair of cavities inthe opposed internal walls of said are shield enclosure on oppositesides of the gap between said arcing contact and immediately adjacentsaid stationary contact bridge and the associated stationary contact,and each said cavity having walls extending perpendicular to thedirection of movement of said arcing contact bridge to prevent depositedcontact material on the interior of said enclosure from establishing anelectrical path between said arcing contact bridge and the associatedstationary contact.

9. In an electric switch, two stationary contacts mounted in spacedapart relation, a movable arcing contact bridge for engaging saidstationary contacts to complete an electrical connection therethrough, amovable current carrying contact bridge for engaging said stationarycontacts to complete an electrical connection therethrough, a movablesupporting member, and means mounting said arcing contactbridge and saidcurrent carrying cona ll ing contact bridge closes the connection firstand opens the connection last and said current carrying contact bridgecloses the connection last and opens the connection first across saidstationary contacts when said supporting member is moved in oppositedirections, and said contact bridges each cause interruption of theconnection between said stationary contacts in two places thereby toafford interruption of higher voltage connections, an arc shield foreach side of said arcing contact bridge, each said are shield comprisingan enclosure of insulating material surrounding and covering theassociated stationary contact and the portion of said arcing contactbridge which engages the latter, and an electrically conducting membermounted within each said enclosure forming with the associatedstationary contact an arc horn diverging from near the point ofengagement between said arcing contact bridge and the associatedstationary contact, said electrically conducting arc horn membercomprising an elongated flat strip having one end adjacent theassociated stationary contact and the other end thereof extending awayfrom said stationary contact, and opposed grooves in the interior wallsof said arc shield enclosure for retaining said strip, and each saidgroove being provided with a wall spaced from the arc-running surface ofsaid fiat strip to provide a slot therealong small enough to prevent theare from entering therein and being effective to prevent the are fromburning the insulated wall of said enclosure.

10. In an electric switch, two stationary contacts mounted in spacedapart relation, a movable arcing contact bridge for engaging saidstationary contacts to complete an electrical connection therethroug'h,a movable current carrying contact bridge for engaging said stationarycontacts tocornplete an electrical connection therethrough, a movablesupporting member, and means mounting said arcing contact bridge andsaid current carrying contact bridge on said supporting member wherebysaid arcing contact bridge closes the connection first and opens theconnection last and said current carrying contact bridge closes theconnection last and opens the connection first across said stationarycontacts when said supporting member is moved in opposite directions,and said contact bridges each cause interruption of the connectionbetween said stationary contacts in two places thereby to affordinterruption of higher voltage connections, an arc shield for each sideof said arcing contact bridge, each said are shield comprising anenclosure of insulating material surrounding and covering the associatedstationary contact and the portion of said arcing contact bridge whichengages the latter, and an electrically conducting member mounted withineach said enclosure forming with the associated stationary contact anarc horn diverging from near the point of engagement between said arcingcontact bridge and the associated stationary contact; each saidstationary contact being provided with a curved surface extending fromthe point of engagement by said 55 arcing contact bridge and formingwith said electrically conducting member a diverging arc horn, and theinterior walls of said are shield enclosure being spaced from oppositeedges of the curved surface of said stationary contact to provide slotstherealong small enough to prevent the are from entering therein andbeing efiective to prevent the are from burning the insulated walls ofsaid enclosure.

-11. In an electric switch, two stationary contacts mounted in spacedapart relation, a movable arcing contact bridge for engaging firstportions of said stationary contacts to complete a first electricalconnection theret-hrough, a movable current carrying contact bridge forengaging second portions of said stationary contacts to complete asecond electrical connection therethrough in parallel with said firstelectrical connection, a pivotal supporting member, means mounting saidcontact bridges on said supporting member to eifect engagement betweenspaced portions of said arcing contact bridge and said first portions ofsaid stationary contacts when said supporting member is pivoted in onedirection and to effect engagement between spaced portions of saidcurrent carrying contact bridge and said second portions of saidstationary contacts when said supporting member is pivoted further insaid one direction, and said mounting means comprising means efiectivewhen said supporting member is thereafter pivoted in the oppositedirection to cause separation of said current carrying contact bridgefrom said second portions of said stationary contacts first andthereafter to cause separation of said arcing contact bridge from saidfirst portions of said stationary contacts, and

said arcing contact bridge causing interruption of theelectrical'connection between said stationary contacts at two points inseries thereby to afford interruption of a higher voltage connection,said mounting means comprising resilient means biasing said currentcarrying contact bridge and said arcing contact bridge independently ofone another, in overlapped relation in that order against saidsupporting member, said resilient means allowing separation of saidarcing contact bridge from said current carrying contact bridgefollowing engagement between said arcing contact bridge and saidstationary contacts and allowing separation of said current carryingcontact bridge from said supporting member following engagement betweensaid current carrying contact bridge and said stationary contacts whensaid supporting member is pivoted in said one direction. 5

References Cited in the file of this patent UNITED STATES PATENTS529,213 Sweet Nov. 13, 1894 1,901,573 Wilms Mar. 14, 1933 2,427,074Scott Sept. 9, 1947 2,945,109 Fehling July 12, 1960 3,031,552 StewartApr. 24, 1962 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 3, 132,225 May 5', 1964 Merle R. Swinehart Column 10, lines59 and 60, for "arcing contact and immediately adjacent said stationarycontact bridge and the associated stationary contact," read arcingcontact bridge and the associated stationary contact and immediatelyadjacent said stationary contact,

Signed and sealed this 15th day of September 1964.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER smsting Officer Commissioner ofPatents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No,3, 132,225 1 May 5-, 1964 Merle R, Swinehart Column 10, lines 59 and 60,for "arcing contact and immediately ad acent said stationary contactbridge and vthe associated stationary contact," read arcing contactbridge and the associated stationary contact and immediately adjacentsaid stationary contact,

Signed and sealed this 15th day of September 1964.

(SEAL) Attcst:

ERNEST SWIDER EDWARD J. BRENNER Aittc's ting Officer Commissioner ofPatents

1. IN AN ELECTRIC SWITCH, TWO STATIONARY CONTACTS MOUNTED IN SPACEDAPART RELATION, A MOVABLE ARCING CONTACT BRIDGE FOR ENGAGING SAIDSTATIONARY CONTACTS TO COMPLETE AN ELECTRICAL CONNECTION THERETHROUGH, AMOVABLE CURRENT CARRYING CONTACT BRIDGE FOR ENGAGING SAID STATIONARYCONTACTS TO COMPLETE AN ELECTRICAL CONNECTION THERETHROUGH, A MOVABLESUPPORTING MEMBER, AND MEANS MOUNTING SAID ARCING CONTACT BRIDGE ANDSAID CURRENT CARRYING CONTACT BRIDGE ON SAID SUPPORTING MEMBER, ANDRESILIENTLY BIASING THEM INDEPENDENTLY AGAINST ONE SIDE OF SAIDSUPPORTING MEMBER IN STACKED RELATION FOR SUCCESSIVE SEPARATION FROM THELATTER AS SAID CONTACT BRIDGE CLOSE AGAINST SAID STATIONARY CONTACTSWHEREBY SAID ARCING CONTACT BRIDGE CLOSES THE CONNECTION FIRST AND OPENSTHE CONNECTION LAST AND SAID CURRENT CARRYING CONTACT BRIDGE CLOSES THECONNECTION LAST AND OPENS THE CONNECTION FIRST ACROSS SAID STATIONARYCONTACTS WHEN SAID SUPPORTING MEMBER IS MOVED IN OPPOSITE DIRECTIONS,AND SAID CONTACT BRIDGES EACH CAUSE INTERRUPTION OF THE CONNECTIONBETWEEN SAID STATIONARY CONTACTS IN TWO PLACES THEREBY TO AFFORDINTERRUPTION OF HIGHER VOLTAGE CONNECTIONS.